This invention relates to a free-jet centrifuge for cleaning the lubricating oil of an internal combustion engine, with a housing closed by a removable cover, with a rotor rotatably arranged in the housing and with channels for feeding the pressurized lubricating oil to be cleaned and for removing the cleaned pressureless lubricating oil, the rotor being of split design with, on the one hand, a drive part having at least one recoil nozzle and, on the other hand, a dirt trapping part having a dirt collection area, with the drive part able to be flowed through by a first partial lubricating oil flow and the dirt trapping part by a second partial lubricating oil flow, with the drive part and the dirt trapping part being designed with positive-interaction torque transmission means which are engageable by axially slipping on the dirt trapping part onto the drive part and disengageable by axially pulling off the dirt trapping part from the drive part, with the dirt trapping part being separable from the drive part for disposal or cleaning, and with means provided or applied in the centrifuge which, in centrifuge operation, serve to prevent or restrict the axial mobility of the dirt trapping part relative to the drive part and which are ineffective or detachable when the cover is removed.
A first free-jet centrifuge is known from DE 200 10 612 U1. With this centrifuge, the rotor housing comprises two parts which are detachably connectable with each other, the drive part comprising first connecting means and the dirt trapping part comprising second, corresponding connecting means. In a concrete embodiment, these connecting means consist of a bayonet lock which can be engaged and disengaged by the limited twisting of the two parts of the rotor against each other.
With this known free-jet centrifuge, it proved to be unfavorable that—for separating the dirt trapping part of the rotor from its drive part—the complete rotor must first be removed from the housing of the free-jet centrifuge and that the two parts of the rotor must then be twisted against each other by applying a certain torque which is required for releasing the bayonet lock. Since the rotor of the free-jet centrifuge in its operation will also be wetted by oil splashes on its outer surface, it is frequently difficult to manually apply the required torque for making and breaking the connection between the two rotor parts. This will require that—especially prior to a separation of the two rotor parts from each other—the exterior surface of the rotor must first be cleaned of adhering oil to then be able to apply the required torque for loosening the bayonet lock. Alternatively, the use of tools is conceivable for which the two rotor parts would then, however, have to be provided, on the one hand, with suitable shoulder areas for one tool each and for which, on the other hand, fitting special tools must be kept available which are engageable with one of the two rotor parts each. In any event, the result will be a time-consuming and complicated handling of the rotor when said rotor is to be separated into its two parts which will be required for every maintenance of the free-jet centrifuge. Moreover, it is considered unfavorable that a sturdy and pressure-proof rotor is here required because the full hydraulic pressure of the lubricating oil to be cleaned prevails on the inside of the rotor since the entire oil stream passed through the centrifuge first flows through the interior of the rotor and is then passed to the recoil nozzles in the drive part.
From DE 43 11 906 A1, a device is known for the ventilation of the crankcase of an internal combustion engine wherein the device comprises a separating device for oil particles entrained with the crankcase gases, the device being connected with a suction line leading to the intake tract. An oil centrifuge provided for the lubricating oil cleaning of the internal combustion engine here serves as the separating device. The rotor of the oil centrifuge comprises two parts which are closely connected with each other in the operation of the centrifuge. The mentioned document does not state anything about the separability of the two rotor parts so that it is assumed that although the rotor parts are manufactured as individual parts, they will be subsequently permanently connected. Accordingly, this document does not disclose a separate disposability of only the dirt trapping part with the dirt deposited therein. With this centrifuge as well, the rotor is under the hydraulic pressure of the lubricating oil to be cleaned, with this hydraulic pressure being specifically used to lift the rotor, in operation, from its lower bearing and press it against an axial bearing provided on the upper side of the rotor and the underside of the housing cover of the centrifuge. For this reason, the rotor must here as well be of a sturdy and pressure-proof design.
From DE 1 012 776 B, another free-jet centrifuge is known in which the rotor is of a two-part design. In this known design, the two parts of the rotor comprise an overlapping area radially on the bottom and outside, in which they are tightly and detachably connected by means of several screws. Thus, a separate disposal or cleaning of only the dirt trapping part of the rotor will actually be possible; yet, the disassembly of the rotor into the dirt trapping part and the drive part is complicated and time-consuming due to the connecting screws which must be individually loosened; the same applies for the subsequent assembly. Moreover, here again a sturdy and pressure-proof rotor is required because the full hydraulic pressure of the lubricating oil to be cleaned prevails on the inside of the rotor since, here again, the lubricating oil first flows through the interior of the rotor and is then passed to the recoil nozzles in the drive part.
From WO 98/46 361 A1, a rotor for a free-jet centrifuge is known, said rotor comprising at least one guiding element which extends from an inner wall to the outer wall of the rotor interior. Due to this guiding element or several such guiding elements, the rotor is to be stiffened such that it will be possible to manufacture it of a plastic material. In accordance with a described embodiment, the rotor is here manufactured of two parts which are connected with each other to the complete rotor, here clipped together. The clip connection means are here designed such that—after the connection has once been made—a non-destructive separation of the two rotor parts will no longer be possible. Such separation is not intended either since the complete rotor being made of a plastic material is to be so inexpensive that it can be completely disposed of after its use without any cost disadvantage. With this known rotor as well, the full hydraulic lubricating oil pressure prevails during operation in its interior because the lubricating oil first flows through the interior of the rotor and is subsequently passed to the recoil nozzles for the drive of the rotor. Thus, here again, a sturdy construction of the rotor is necessary to achieve the required pressure resistance.
DE 1 105 351 B discloses a free-jet centrifuge which—in deviation from the usual arrangement—has the characteristic feature that the drive part with the recoil nozzles forms an upper part of the rotor and that the dirt trapping part of the rotor forms its lower part. The two rotor parts are connected with each other in a sealing and detachable manner by means of several connecting screws. Here again, there is the disadvantage that—for a disassembly of the rotor—the latter must first be completely removed from the housing and that, thereafter, several screws must be removed before the dirt trapping part can be separated from the drive part. The assembly requires the same great expenditure so that simple and fast maintenance of the centrifuge will not be possible. Moreover, the rotor must here again be of a sturdy and pressure-proof design since it is subject to the full lubricating oil pressure because, here too, the lubricating oil first flows through the interior of the rotor and subsequently through the recoil nozzles.
WO 00/23 194 A1 shows a centrifuge comprising a split rotor. The two parts of the rotor can be either screwed together, thus enabling subsequent separation, or they can be permanently fused or welded with each other. In the separable design, a separation of the rotor is used for the installation of a rotor insert and later, after a certain operating period, for the inspection and replacement of the rotor insert, as needed. With this known centrifuge, the drive is provided spatially at a distance from the rotor and consists either of a turbine or an electrical motor. Both drives are very complicated—compared with recoil nozzles on the rotor—and will not only result in higher manufacturing costs but also in a larger installation space for the centrifuge. This is in contradiction to the generally desired compact construction and low-cost manufacturability.
The prior DE 10 2004 005 920 A1 without prior publication shows a rotor assembly to be used as part of a centrifuge for the separation of particle-like material from a fluid. The rotor assembly comprises a collection chamber, housing a particle separation device, as well as a drive chamber with a Hero-turbine. The drive chamber can be assembled with the collection chamber and is separable from it. The fit between the drive chamber and the collection chamber transmits any rotary movement of the drive chamber caused by the Hero-turbine directly to the collection chamber for particle separation. Due to the drive chamber being separable from the collection chamber, the collection chamber can be disposed of with the sludge accumulated in it.
It is considered detrimental with this known rotor assembly that the drive chamber is completely outside, here underneath, the collection chamber. This brings about that—aside from two bearings provided in the area of the drive chamber—a third bearing will always be required at the end of the collection chamber away from the drive chamber, here the top end, to ensure adequate bearing with good true running of the collection chamber. This third bearing results in increased manufacturing and installation expenditures and in additional weight. Furthermore, it is considered detrimental that—with every removal and installation of the collection chamber—the upper, third bearing will be under mechanical stress which is unfavorable for its lifetime. Thus, there is the risk that the third bearing—in time—will have an increased coefficient of friction which will result in a reduction of the otherwise achievable speed of the rotor. Finally, it should be mentioned as a disadvantage that—upon a removal of the collection chamber from the housing of the centrifuge—it will not be ensured that the drive chamber will safely remain within the centrifuge. Much rather, it might inadvertently happen that, upon removal of the collection chamber, the drive chamber will also be removed, whereby the two bearings of the drive chamber will be exposed to undesirable mechanical stress. Here again, any damage of the bearings will result in an increased bearing friction and a reduction of the achievable speed of the rotor at a specified drive power.